The present invention generally relates to wireless communication devices, and more specifically, to improving the localization of wireless communication devices.
There has been an increasing demand for reliably locating wireless communication devices. In some cases, the wireless communication devices themselves need to be located, e.g., for maintaining a connection to a communication network, and in other cases, the wireless communication devices are attached to items which need to be located. Similarly, it can also be desired to locate the position of a person carrying a wireless communication device. Different applications based on location information are already available. Such location based services include securing or tracking access to specific areas, or to providing information related to the current location of a person using the wireless communication device.
Different technologies are used in the art for locating wireless communication devices. These technologies depend also on the kind of communication technology used in the wireless communication device and the transceiver infrastructure. The common concept of locating a device is based on triangulation, which requires a set of at least three transceivers to receive a signal from the wireless communication device to be located in order to determine a three dimensional (3D) position. Depending on the triangulation technology that is used, a set of four transceivers may be the minimum number of required transceivers.
Triangulation can be used independently from the underlying communication technology and can be applied to ultrasonic, optical or radio communication technologies including: wireless local area networks (LANs) (e.g., wireless LANs or “WLANs”, and wireless fidelity or “WIFI”), Bluetooth technology and Radio Frequency Identification (RFID). When receiving the signal from the wireless communication device, different measurements like the time of arrival (TOA) of the signal at the different transceivers, the time difference of arrival (TDOA), an angle of arrival (AOA) and/or a received signal strength indicator (RSSI) can be used to locate a wireless communication device by means of triangulation.
Reliably determining the position of a wireless communication device depends on the provided transceiver infrastructure. The transceivers have to be located to cover the whole area in a way so that from each point of the area, a signal from the wireless communication device to be located can be received by at least three transceivers. This is rather simple in plane territory but can be complicated in areas having obstacles therein, e.g., mountains, bridges, houses, or when talking about smaller areas, obstacles like walls, persons or whatever. These obstacles in general can, for example, absorb or reflect communication signals and limit the coverage of communication signals within the covered area. In the case of radio communication, especially obstacles made of metal can cause communication problems. In addition, emitters which are emitting within the covered area, can cause interference and thereby reduce the coverage within the area. These emitters can be other wireless communication devices sending similar signals, or any kind of other emitters which have emissions that can interfere with the communication between the wireless communication device and the transceivers. When the coverage is reduced, either the position of a wireless communication device cannot be determined at all or, as long as communication with at least a reduced number of transceivers is possible, the position is determined with reduced accuracy (also referred to as a margin of tolerance).